Adaptive communication systems and methods

ABSTRACT

Methods and communication systems are presented, in which impulse noise is monitored on a communication channel, and impulse noise protection parameters are adjusted according to the monitored impulse noise without interrupting communication service.

FIELD OF INVENTION

The present invention relates generally to communication systems andmore particularly to adaptive communication methods using DigitalSubscriber Line (DSL).

BACKGROUND OF THE INVENTION

Digital subscriber line (DSL) technology provides high-speed datatransfer between two modems across ordinary telephone lines, whereindigital data transfer rates from tens of Kbps to tens of Mbps aresupported over standard (e.g., twisted pair) telephone lines, whilestill providing for plain old telephone service (POTS). AsynchronousDigital Subscriber Line (ADSL) and Very High Digital Subscriber Line(VDSL) have emerged as popular implementations of DSL systems, whereADSL is defined by American National Standard Institute (ANSI) standardT1.413 and International Telecommunication Union (ITU-T) standardsG.992.3, G.992.5, and VDSL is defined by ANSI standard T1.424 and ITU-Tstandard G.993.1. ADSL, VDSL and other similar DSL systems (collectivelyreferred to as “xDSL”) typically provide digital data transfer in afrequency range above the POTS band (e.g., about 300 Hz to 4 kHz), forexample ADSL G.992.3 operates at frequencies from about 25 kHz to about1.1 MHz.

Most DSL installations are operated as multicarrier systems usingDiscrete Multi Tone (DMT) modulation, in which data is transmitted by aplurality of subcarriers (tones), sometimes alternatively referred to assubchannels, sub-bands, carriers, or bins, with each individualsubcarrier utilizing a predefined portion of the prescribed frequencyrange. In ADSL, for example, 256 subcarriers are used to transmit a DMTsymbol, with each subcarrier having a bandwidth of 4.3125 kHz. Thetransmit digital data is encoded and modulated at the transmitter usingQuadrature Amplitude Modulation (QAM) and Inverse Discrete FourierTransform (IDFT) to create the modulated multicarrier signal fortransmission along the DSL loop or channel, which is then demodulated atthe receiving end and decoded to recover the transmitted data. The bitsof data to be transmitted over each subcarrier are encoded as signalpoints in QAM signal constellations using an encoder or a bit mappingsystem. Signal constellations are then modulated onto the correspondingsubcarrier. The total number of data bits transmitted over the channelis a sum of the bits transmitted by each subcarrier.

As in most types of communication systems, it is desirable to maximizethe amount of data successfully transferred across the communicationmedium between DSL modems, sometimes referred to as the bit rate or datarate. The data rate, in turn, depends on the noise characteristics of aparticular communication channel. In the case of DSL systems, a pair ofmodems is connected by a twisted pair of wires that form thecommunication medium. In this situation, noise may be generated bysignals on neighboring wire pairs (e.g., crosstalk noise) in adistributed telephony system, as well as by outside sources of RadioFrequency Interference (RFI) or other noise. The noise on a particularcommunication channel may be generally modeled or characterized ascontinuous noise or impulse noise or both. Continuous noise is sometimesmodeled as Additive Gaussian Noise (AGN) with randomly distributedvalues of noise over time, whereas impulse noise is generally shortbursts of relatively high levels of channel noise. Various mechanisms ortechniques are employed in DSL and other communication systems to combatcontinuous and impulse noise and/or to correct noise-related datatransfer errors.

Continuous noise is typically addressed by transmitting more data bitsover subcarriers with small amounts of continuous noise, and fewer databits over subcarriers with higher continuous noise. The allocation ofdata bits to particular subcarriers is sometimes referred to as bitallocation or bit distribution, wherein the bit distribution parametersmay be set to accommodate particular continuous noise conditions on thechannel. However, simply maximizing continuous noise protection byreducing the number of bits transmitted by specific sub-carriers maylead to non-optimal system data rate, since maximizing continuous noiseprotection in this way reduces the number of data bits on thesubcarriers. Accordingly, DSL systems are initially setup withcontinuous noise protection (e.g., bit distribution) settings orparameters that are selected according to subcarrier noise assessmentsbased on estimation of the channel noise during system initialization.While such approaches using fixed continuous noise protection settingsprovide a good continuous noise protection and high data transfer rates,communication channel continuous noise conditions tend to change overtime. In this regard, if the continuous noise decreases, the fixedmodulation parameters will suffice to protect against data errors, butpotential increased data rates are not attained. Conversely, if thecontinuous noise increases, the previously set protection parameters mayno longer be sufficient to provide adequate protection against datatransfer errors in the channel.

In order to address this situation, DSL systems provide adaptive tuningof the bit distribution parameter settings to accommodate changing ofcontinuous noise, including bit swapping, rate adaptation, and bandwidthrepartitioning techniques, each of which involve changes to a number ofmodulation parameters. In a typical situation, the signal-to-noise ratio(SNR) for each subcarrier is measured during system initialization, andthe maximum bit capacity of each subcarrier is determined. Once thetransmission capability of the system is thus assessed, more bits (e.g.,larger constellation sizes) are assigned onto subcarriers with higherSNR compared to subcarriers having lower SNR and the subcarrier relativetransmit powers (gains) are set. DSL service is then begun and thesubcarriers SNR are measured during data transmission; the bitre-distribution (bit swapping) being performed and subcarrier gainsbeing adjusted according to changes in the subcarrier SNR measurements.

Bit swapping by itself does not change the total data rate of thecommunication channel, but serves to increase or maintain continuousnoise immunity by reallocating data bits from noisy subcarriers to morenoise-free subcarriers. Where the channel noise increases significantly,bit swapping alone may not be adequate to prevent data transmissionerrors, and seamless rate adaptation (SRA) may be employed to decreasethe number of data bits transmitted over some subcarriers. If thechannel continuous noise thereafter decreases (e.g., SNR increases), SRAcan then be used to increase the number of data bits. While thesetechniques can effectively react to changing continuous noiseconditions, impulse noise protection is largely unaffected by bitdistribution settings and seamless rate adaptation.

Impulse noise in DSL systems usually causes erasure of an entiremodulated signal for a relatively short period of time, regardless ofthe number of bits allocated to the entire channel or to particularsubcarriers. Forward error correction (FEC) is a means to combat impulsenoise in DSL and other communication systems. An FEC encoder generates acertain amount of redundancy bytes for each block of transmitted databytes. The redundancy bytes are then added to the data bytes to form anFEC codeword. At the receive side, the FEC decoder uses redundancy bytesfor recovering (correcting) a certain amount of corrupted data bytes,and thereby ensures that when a small number of bytes in a codeword arecorrupted, the original data transmitted in the codeword can berecovered. In general, the number of error bytes that can be correctedby FEC is half of the number of redundancy bytes included in thecodeword. Thus, increasing FEC redundancy adds further FEC protectionagainst impulse noise while effectively decreasing the data rate, andvice versa, wherein the goals of impulse noise protection and data rateinvolve a tradeoff.

In addition to redundancy, FEC encoders also provide interleaving (IL)to combat impulse noise. An interleaver (at the transmit side) segmentsthe FEC codewords into smaller portions (segments) after the addition ofFEC redundancy bytes, with segments from different codewords being mixedin a certain order prior to bit distribution and modulation. The orderof segment mixing is so that segments belonging to the same FEC codewordare placed as far as possible from each other. This results in the bytesof the same codeword being spread out over time, whereby impulse noisecorruption of the transmitted stream of data during any given shortperiod of time results in corruption of only one or a few segmentsbelonging to a particular codeword, causing fewer errors in eachreassembled (e.g., de-interleaved) codeword at the receive side. Thus,FEC redundancy allows correction of a certain amount of corrupted datain each codeword, and interleaving helps to reduce the amount ofcorrupted bytes in the individual codewords, whereby DSL systems mayeffectively combat a given amount of impulse noise in the communicationchannel. However, interleaving requires buffer memory at the transmitterand receiver modems and introduces latency in the transferred data.Also, as discussed above, increasing FEC capabilities requires moreredundancy bytes to be introduced, and reduces the data rate. Thus,there is a tradeoff between impulse noise protection and data rate inDSL systems.

The parameters for impulse noise protection mechanisms, such as FEC andIL in DSL systems, have conventionally been set up at systeminstallation. However, the current field experience shows that impulsenoise characteristics for any specific installation are almostunpredictable and changing in time. Therefore, it is usually unclear howthe impulse noise protection has to be set. In one example, the impulsenoise parameters (e.g., the number of FEC redundancy bytes and the levelor amount of data interleaving) are maximized, and left unadjusted asDSL service is provided, resulting in reduced DSL data rate. Recentproposals suggest iterative adjustment of FEC/IL parameters duringinitialization, by repeating the initialization procedure several timeswith different settings. This is also not comprehensive, since itincreases initialization time, which makes the system inconvenient forthe user. Moreover, this proposal fails to provide good settings becausethe time over which the multiple parameter adjustments are done isrelatively short considering that impulse noise conditions may changeover a period of hours or days. Thus, the multiple initialization timeis still very short to observe changes in the impulse noise conditions.As a result, we see that impulse noise conditions may change over time,wherein excessive FEC/IL protection settings unnecessarily sacrificedata rate if the impulse noise is reduced, while limited FEC/ILprotection risks unwanted data loss when the impulse noise situationworsens. Accordingly, there is a need for improved impulse noiseprotection methods and apparatus to combat changing impulse noise intransmission channels of DSL and other communication systems, whileallowing maximum data rates.

SUMMARY OF THE INVENTION

The following presents a simplified summary in order to provide a basicunderstanding of one or more aspects of the invention. This summary isnot an extensive overview of the invention, and is neither intended toidentify key or critical elements of the invention, nor to delineate thescope thereof. Rather, the primary purpose of the summary is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

The present invention involves communication systems and methods foradaptive adjustment of a DSL or other communication systems, in whichimpulse noise on a communication channel is monitored during thecommunication service, and impulse noise protection is selectivelyadjusted according to the impulse noise without interrupting thecommunication service. The invention facilitates tailoring impulse noiseprotection such as codeword format changes including the number andlocation of forward error correction redundancy bytes and codeword size,and/or adjustment of interleaving to accommodate or compensate forchanging impulse noise conditions in DSL or other communication systems,so as to protect against data errors without unnecessarily sacrificingdata rate.

One aspect of the invention provides a method for adaptive adjustment ofa communication system. The method comprises monitoring impulse noise ona communication channel during the communication service, andselectively adjusting impulse noise protection according to the impulsenoise without interrupting the communication service. In oneimplementation, the impulse noise is monitored by monitoring datatransfer errors occurring on the communication channel, determiningwhether any of the data transfer errors are packetized errors, anddetermining whether any such packetized errors are corrected oruncorrected. The selective adjustment of the impulse noise protectionmay comprise selectively increasing the impulse noise protection ifthere are uncorrected packetized errors, and selectively decreasing theimpulse noise protection if there are no uncorrected packetized errorsand the number of corrected packetized errors is less than a thresholdvalue (including no packetized errors at all, corrected or uncorrected),wherein the impulse noise protection is left unchanged if there are nouncorrected packetized errors during sufficiently long time intervals,and the number of corrected packetized errors is less than or equal tothe threshold value.

Another aspect of the invention provides a method for adaptiveadjustment of a communication system, comprising monitoring impulsenoise as well as continuous noise on the communication channel duringcommunication service, and selectively adjusting impulse noiseprotection and continuous noise protection in the system according tothe impulse noise and the continuous noise without interrupting thecommunication service. In one example, bit swapping and/or seamless rateadaptation are performed to adjust for changing continuous noiseconditions, and FEC/IL and codeword size parameters are selectivelyadjusted according to impulse noise conditions, wherein the impulsenoise protection and the continuous noise protection are adjusted in acoordinated fashion to minimize redundancy.

Yet another aspect of the invention provides a communication system,comprising a communication channel and first and second modems coupledwith the communication channel, where the receiving modem is adapted tomonitor impulse noise on the communication channel during thecommunication service. The modems cooperatively adjust impulse noiseprotection according to the observed impulse noise characteristicswithout interrupting the communication service. In one implementation,the receiving modem also monitors continuous noise on the communicationchannel during the communication service, wherein the first and secondmodems are adapted to cooperatively adjust impulse noise protection andcontinuous noise protection in the system according to the observedimpulse noise and the continuous noise characteristics withoutinterrupting the communication service.

Still another aspect of the invention provides a modem, comprising atransceiver, a monitor system, and an analyzer system. The transceiveris coupleable to a communication channel and supports communicationservice with a second modem on the communication channel. The monitorsystem monitors data transfer errors occurring on the communicationchannel during communication service, and the analyzer system determineswhether any of the data transfer errors are packetized errors, and alsowhether any packetized errors are corrected or uncorrected. The analyzeris further adapted to propose impulse noise protection adjustments tothe second modem according to the observed impulse noise characteristicsand to cooperatively adjust impulse noise protection according to theimpulse noise without interrupting the communication service.

The following description and annexed drawings set forth in detailcertain illustrative aspects and implementations of the invention. Theseare indicative of only a few of the various ways in which the principlesof the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an exemplary multicarrier DSLcommunication system with first and second DSL modems coupled with acommunication channel or loop in accordance with one or more aspects ofthe present invention;

FIG. 2 is a flow diagram illustrating a simplified method of adjusting acommunication system for adapting to changing impulse noise inaccordance with the invention;

FIG. 3 is a detailed flow diagram illustrating a more detailed method ofadjusting a communication system for adapting to changing impulse noisein accordance with the invention;

FIG. 4 is a detailed flow diagram further illustrating increasingimpulse noise protection in the method of FIG. 3;

FIG. 5 is a detailed flow diagram further illustrating increasingefficiency by decreasing unnecessary impulse noise protection in themethod of FIG. 3;

FIG. 6 is a flow diagram illustrating a simplified method of adjusting acommunication system for changing impulse noise and/or changingcontinuous noise in accordance with the invention; and

FIGS. 7A and 7B provide a flow diagram illustrating a more detailedmethod of adjusting a communication system for changing impulse noiseand/or changing continuous noise in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

One or more implementations of the present invention will now bedescribed with reference to the attached drawings, wherein likereference numerals are used to refer to like elements throughout. Theinvention relates to communication systems and methods for adaptiveadjustment of system parameters to combat impulse noise, which ishereinafter illustrated in the context of an exemplary DSL multicarriercommunication system using Discrete Multitone Transmission (DMT)modulation with Forward Error Correction (FEC) comprising Interleaving(IL), and their parameters adjustment for impulse noise protection, aswell as bit swapping and rate adaptation for continuous noiseprotection. However, the invention finds utility in association with anytype of communication systems, including but not limited to DSL systems,and single or multicarrier communication systems wherein any type ofimpulse noise protection techniques may be employed and dynamicallyadjusted according to impulse noise conditions. The invention involvesmonitoring impulse noise conditions and adjusting impulse noiseprotection parameters during the provision of communication services,wherein the various aspects of the invention may be carried out alone orin combination with initialization adjustments in a communicationsystem. In this regard, the acts occurring during communication servicein accordance with the invention are distinct from those occurring in asystem initialization, wherein initialization involves exchange ofcontrol and/or test signals or information for a limited period of time,whereas communication service involves transfer of user data orinformation that may continue for very long periods of time. Theinvention may thus provide for continuous adaptation of impulse noiseprotection for changing noise conditions, whereas conventionalinitializations measure noise only for a short time and then provide onefixed set of parameters.

FIG. 1 illustrates an exemplary multicarrier DSL communication system 2in which one or more aspects of the invention may be implemented,comprising first and second DSL modems 10 and 30, respectively, coupledwith a communication loop or channel 4. The exemplary communicationchannel 4 is a twisted pair or copper wires in a conventionalresidential telephone system, although the invention may be employed incommunication systems employing any type of communication channel 4 bywhich data can be transferred between the modems 10 and 30. Theexemplary modems 10 and 30 are DSL modems having suitable circuitry forproviding DSL communication service on the channel 4 generally inaccordance with ANSI T1.413 (ADSL), T1.424 (VDSL) and other DSLstandards, including performance of the tasks and functions describedherein.

In the illustrated system 2, the first modem 10 is a subscriber modemthat may be located in a residential home, and the second modem 30 islocated at a DSL service provider. Data is transferred in bothdirections along the channel 4, wherein the subscriber modem 10transmits data to be received by the provider modem 30 and the providermodem 30 transmits data to be received by the subscriber modem 10. Inthis regard, the exemplary communication system 2 is symmetrical,although the various aspects of the invention may be carried out inother systems in which data is transferred in a single direction only.In order to appreciate the various aspects of the invention, theexemplary system 2 and the various methods of the invention arehereinafter described with respect to data being transferred in a firstdirection from the provider modem 30 to the subscriber modem 10.Accordingly, in the following discussion, the first modem 10(specifically, a transceiver 18 thereof) may be referred to as a“receiver” and the second modem 30 (specifically, a transceiver 38thereof) may be referred to as a “transmitter” for purposes ofdescribing the various aspects of the invention, with the first(receiver) modem 10 monitoring and analyzing continuous and impulsenoise and proposing noise protection parameter changes to the second(transmitter) modem 30, which then institutes the changes. However, itwill be appreciated that both modems 10 and 30 are capable oftransmitting and receiving data in the illustrated implementation,wherein the modems 10 and 30 may both be configured to monitor noisewith respect to data received thereby and to selectively propose and toinstitute noise protection parameter changes in a cooperative mannerwith the other modem.

In the exemplary system 2, the first modem 10 is adapted to monitorimpulse noise (e.g., corrected and uncorrected packetized errors, etc.)with respect to data received on the communication channel 4 from thesecond modem 30 during communication service. The first modem 10analyzes the monitored impulse noise and selectively proposesappropriate noise protection parameter changes to the second modem 30.The modems 10 and 30 are adapted to cooperatively adjust impulse noiseprotection for transferring data from the modem 30 to the modem 10(e.g., by selectively adjusting the codeword format including the numberof FEC redundancy bytes and/or the codeword size, and/or by selectivelyadjusting the amount of interleaving,) according to the observed impulsenoise without interrupting the communication service. In accordance withanother aspect of the invention, moreover, the exemplary first modem 10is further adapted to monitor continuous noise with respect to datareceived from the second modem 30 (e.g., SNR, non-packetized errors,etc.) on the communication channel 4 during the communication service,wherein the modems 10 and 30 are further adapted to cooperatively adjustimpulse noise protection and continuous noise protection in the systemaccording to the impulse noise and the continuous noise in a coordinatedfashion to minimize redundancy without communication serviceinterruption.

The exemplary first modem 10 comprises a transceiver 18 that iscoupleable to the channel 4 and operates to support communication (e.g.,DSL) service with the second modem 30. With respect to received datafrom the second modem 30, the transceiver 18 operates to receive suchdata from the channel 4. The first modem 10 also comprises anapplication interface 12 to a host system, such as a servicesubscriber's home computer (not shown), wherein the second modem 30 alsocomprises an application interface 32 with a network node (not shown).The FEC system 14 of the first modem 10 comprises an FEC decoder and ade-interleaver operating in conjunction with an FEC controller 16,wherein the forward error correction (FEC) system 34 of the second modem30 includes an FEC encoder and an interleaver with a corresponding FECcontroller 36, where the FEC system 34 provides redundancy bytes tooutgoing data when transmitting to the first modem 10. The FEC system 14of the receiving first modem 10, in turn, uses received redundancy bytesto correct errors in incoming data (when receiving data from the secondmodem 30). In a bidirectional setting, the FEC system 14 of the firstmodem 10 further provides selective interleaving and encoding ofoutgoing data (when transmitting data to the second modem 30) and theFEC system 34 of the second modem 30 provides de-interleaving ofincoming data (when receiving data from the second modem 30), whereinthe exemplary FEC systems 14 and 34 each comprises suitable logiccircuits for controlling the FEC/IL functions described herein, as wellas memory for buffering data to be interleaved/de-interleaved.

The transceiver 18 of the first modem 10 provides demodulation ofincoming data from the second modem 30, and includes suitable analogcircuits for interfacing with the communication channel 4 for receipt ofincoming data. In the second modem 30, the transceiver 38 provides fortone ordering or bit distribution, wherein outgoing data bits to betransmitted over each subcarrier are encoded as signal points in signalconstellations using bit distribution parameters provided by a bitdistribution controller 40. The transceiver 38 of the second modem 30also modulates the outgoing subcarrier constellations (in the presentedexample using inverse discrete Fourier transform (IDFT)) and providesthe modulated signals to the channel 4 according to subcarrier gainscale settings from the controller 40. For incoming data received fromthe second modem 30, the transceiver 18 of the first modem 10demodulates the received signals into individual subcarrierconstellations (e.g., by discrete Fourier transform or DFT techniques inthe presented example), and decodes the received constellationsaccording to the parameters from a corresponding bit distributioncontroller 20.

The first modem 10 also includes a local management system 22 thatprovides the FEC/IL parameters to the FEC controller 16 for the numberof redundancy bytes in the received data and the amount or level ofde-interleaving thereof, and also provides the bit distribution settingsor parameters to the controller 20, including subcarrier bitallocations, gain settings, etc. for decoding and demodulation of theincoming data received from the channel 4. The FEC system 14 thenperforms de-interleaving and error correction according to parametersfrom the FEC controller 16, and provides the resulting incoming data tothe application interface 12.

The second modem 30 implements similar functionality with respect tonormal DSL communication service, and comprises a transceiver 38 coupledwith the channel 4, a bit distribution system 40 that controls themodulation (demodulation) and encoding (decoding) of data in thetransceiver 38. The second modem 30 further comprises an applicationinterface 32 for interfacing to a host system (not shown), as well as anFEC system 34 and a corresponding FEC controller 36 for providing datainterleaving and forward error correction functions similar to thosedescribed above with respect to the first modem 10. The second modem 30also includes a local management system 42, providing control parametersand settings to the FEC controller 36 and to the bit distributioncontroller 40.

The local management systems 22 and 42 of the first and second modems 10and 30, respectively, exchange control information and messages with oneanother via a local management channel 46, such as one of thesubcarriers of the communication channel 4 using any suitablecommunication or data exchange protocol, so as to coordinate parameterssettings, rate adjustments, timing of changes, etc. In particular, thelocal management systems 22 and 42 exchange bit distribution and gainsettings for use by the respective bit distribution controllers 20 and40, as well as FEC/IL and codeword size settings for use by therespective FEC controllers 16 and 36. In the illustrated system 2, thelocal management systems 22 and 42 exchange settings and information viathe management channel 46 during system initialization for establishinginitial subcarrier bit capacities and gain settings based on initialmeasurements of the subcarrier continuous noise levels (e.g., SNR). Forinstance, during initialization, the signal-to-noise ratio (SNR) foreach subcarrier is obtained, and the maximum bit capacity of eachsubcarrier is determined by one of the modems 10, 30. This informationis sent to the other modem, such that upon initiating DSL service, themodems are using the same parameters. Likewise, FEC/IL parameters andcodeword size are initially set by one of the modems, according toinitial noise measurements or according to some other criteria (e.g.,max protection), with the settings being replicated to the other modemvia the management channel 46.

In accordance with the present invention, the exemplary first modem 10also comprises a noise and error monitor system 24 and an analyzer 26,wherein the monitor system 24 monitors data transfer errors occurring onthe communication channel 4 for incoming data received from the secondmodem 30 via error information from the FEC system 14 during DSLservice, and the analyzer 26 determines whether the incoming datatransfer errors indicate the presence of impulse noise on the channel 4.In particular, the analyzer 26 determines whether any of the incomingdata transfer errors are packetized errors (e.g., relatively largeerrors of short duration), and whether such packetized errors arecorrected or uncorrected by the FEC system 14. Either or both of theanalyzer 26 and the monitor system 24, and/or any of the othercomponents of the first modem 10 illustrated in FIG. 1 may be fabricatedtogether with the transceiver 18 as a single integrated circuit. It isnoted that the exemplary second modem 30 also comprises noise monitoringand analyzing components (not shown) for monitoring and analyzing noiseand data transfer errors for data transferred from the first modem 10 tothe second modem 30, wherein the various impulse noise protectionadjustment features of the invention are provided for data beingtransferred in both directions along the channel 4 in the exemplarysystem 2.

As illustrated and described further below with respect to FIGS. 2-5,based on the assessment of the impulse noise situation on the channel 4for data received in the first modem 10, the analyzer 26 selectivelyrecommends changes to the impulse noise protection to the localmanagement system 22 (e.g., changes to FEC/IL parameters and codewordsize in this example). The management system 22, in turn cooperativelyinteracts with the corresponding management system 42 of the secondmodem 30 to coordinate synchronized implementation of such changes ofimpulse noise protection parameters in the system 2 without interruptingthe communication service. The management system 42, in turn, promptsthe second modem 30 to provide time markers 44 for FEC and bitdistribution changes to co-ordinate changes in the settings of bothmodems without service interruption on the channel 4.

In particular, the analyzer 26 analyzes received data error informationand suitable statistics based thereon, and recommends increasing impulsenoise protection (e.g., increasing interleaving within memory and/orlatency limitations, increasing the number of FEC redundancy bytes,and/or decreasing codeword size) if the current impulse noise protectionis deemed to be ineffectual based on the current impulse noise situation(e.g., uncorrected packetized errors). The analyzer 26 may alternativelyrecommend decreasing impulse noise protection to increase efficiency ofthe system (e.g., increasing codeword size, decreasing FEC redundancy,and/or decreasing interleaving) if the current impulse noise protectionis deemed to be excessive for the current impulse noise situation (e.g.,no uncorrected packetized errors and corrected packetized errors lessthan a threshold value). Furthermore, the analyzer 26 may suggest toleave the FEC/IL and codeword size settings unchanged if it isdetermined that the current protection is adequate and not excessive. Inthis manner, the system 2 provides for dynamic optimization of thetradeoff between impulse noise protection and data rate to a muchgreater extent than it was possible in conventional systems in which theimpulse noise settings were left unchanged during DSL service.

In addition to the adaptive impulse noise protection adjustments of theinvention, the exemplary modems 10 and 30 may also provide for adaptiveadjustment to continuous noise protection, wherein the continuous noiseand impulse noise parameter adjustments may be coordinated so as tominimize system redundancy, as illustrated and described in greaterdetail below with respect to FIGS. 6-7A. In this regard, the noise anderror monitor 24 of the exemplary first modem 10 also monitorscontinuous noise in the subcarriers of the communication channel 4, andthe analyzer 26 proposes changes to the continuous noise protectionparameters accordingly. These parameter changes can involve any form ortype of continuous noise protection, including but not limited to bitswapping and seamless rate adaptation techniques, wherein the protectionmay be increased at the expense of data rate, or the protection may bereduced to improve the data rate.

Referring now to FIGS. 2-5, exemplary methods are illustrated forselective adjustment of impulse noise protection in a communicationsystem in accordance with the present invention, wherein FIG. 2illustrates a simplified method 50 and a more detailed method 100 isillustrated in FIGS. 3-5. In this regard, the various components of thesystem 2 above and other systems of the invention include suitablecircuitry, state machines, firmware, software, logic, etc. to performthe various methods and functions illustrated and described herein,including but not limited to the exemplary methods described below.While the methods 50 and 100 and other methods of the invention areillustrated and described below as a series of acts or events, it willbe appreciated that the present invention is not limited by theillustrated ordering of such acts or events. For example, some acts mayoccur in different orders and/or concurrently with other acts or eventsapart from those illustrated and/or described herein, in accordance withthe invention. In addition, not all illustrated steps may be required toimplement a methodology in accordance with the present invention.Furthermore, the methods according to the present invention may beimplemented in association with the operation of communication systemswhich are illustrated and described herein (e.g., the system 2 in FIG. 1above) as well as in association with other systems not illustrated,wherein all such implementations are contemplated as falling within thescope of the present invention and the appended claims.

In the method 50 of FIG. 2, DSL service begins at 52, and impulse noiseis monitored at 54 during the DSL service. It is noted at this pointthat the impulse noise monitoring, analysis, and selective protectionparameter adjustment features of the invention are undertaken after DSLservice has begun. Moreover, the techniques of the present invention maybe employed alone or in combination with pre-DSL service parameteradjustments or initialization routines such as those described above. Asillustrated and described below with respect to FIGS. 3-5, the impulsenoise may be monitored during DSL service by accumulating statistics ofdata transfer errors (e.g., in the noise and error monitor system 24 ofFIG. 1) and analyzing such statistics with respect to the existence ofpacketized errors (e.g., in the analyzer system 26 of FIG. 1), includingwhether and how many such packetized errors have occurred in the channel4 and how many of these are corrected and/or uncorrected by the currentFEC redundancy settings. Other suitable monitoring and analysistechniques may be employed at 54 and 56, by which the existence andseverity of channel impulse noise is ascertained, wherein all suchvariant implementations are contemplated as falling within the scope ofthe invention and the appended claims.

At 56-62, the impulse noise protection is selectively adjusted oradapted according to the monitored impulse noise in the channel withoutinterrupting the communication service. At 56, a determination is madeas to whether the current impulse noise protection is adequate orsufficient, based on the monitored impulse noise. If not (NO at 56), theimpulse noise protection is selectively increased at 58 withoutinterrupting the DSL service, and the method 50 returns to 54 tocontinue impulse noise monitoring. In the detailed examples illustratedand described below with respect to FIGS. 3-5, interleaving levels, FECredundancy, and codeword size are adjusted to change the impulse noiseprotection. However, any single operational parameter or multipleoperational parameters of a communication system may be adjusted at 58by which protection against impulse noise is increased, wherein all suchalternative implementations are contemplated as falling within the scopeof the invention and the appended claims. In this regard, the method 50and other methods of the invention facilitate adaptive adjustmentwithout service interruption to accommodate situations where channelimpulse noise worsens or improves after DSL service has begun. Thus,even where the parameters are initially tuned or selected according toan initial characterization of the noise environment, the presentinvention advantageously provides dynamic adjustment to facilitateoptimal tradeoff between current noise conditions that change from timeto time and system efficiency to an extent not possible using priortechniques.

If the current impulse noise protection is sufficient (YES at 56), adetermination is made at 60 as to whether the impulse noise protectioncan be safely reduced. If so (YES at 60), the impulse noise protectionis selectively decreased at 62 without service interruption, and themethod 50 returns to 54 to continue impulse noise monitoring. In theexemplary implementations illustrated and described below with respectto FIGS. 3-5, interleaving levels are decreased, FEC redundancy isdecreased, and/or codeword size is increased to reduce the impulse noiseprotection. However, any single or multiple operational parameters of acommunication system may be adjusted at 62 by which excess protectionagainst impulse noise is reduced, wherein all such alternativeimplementations are contemplated as falling within the scope of theinvention and the appended claims. In this manner, the method 50facilitates improvement in system efficiency (e.g., increased data rateby decreased impulse noise protection) in situations where the channelimpulse noise decreases. If the impulse noise protection cannot besafely reduced, (NO at 60), the method returns to monitor impulse noiseat 54 without adjusting the impulse noise protection settings.

Referring now to FIGS. 1 and 3-5, a more detailed method 100 isillustrated and described hereinafter for adjusting a communicationsystem in accordance with the invention. At 102 in FIG. 3, initialimpulse noise protection parameters are set. For example, in the system2 of FIG. 1, the number of FEC redundancy bytes, the amount ofinterleaving, and the initial codeword size may be set by the FECcontrollers 16 and 36 in the first and second modems 10 and 30,respectively. This may be a single fixed setting of the level ofinterleaving, number of FEC redundancy bytes, and codeword size, forexample, to maximize the initial protection against impulse noise, ormay by done based on an initial measurement, estimate, or otherassessment of the impulse noise conditions in the channel 4 during theinitialization, or may be an iterative initialization process to set theinitial FEC/IL and codeword size parameters, such as the above-describedtechniques, after which DSL service begins at 104.

At 106, data transfer errors are monitored by the first modem 10,wherein the noise and error monitor system 24 obtains data transfererror information from the FEC system 14 relating to errors detected andcorrected in incoming data from the channel 4. In the illustratedsystems, this error data indicates the number of errors detected by theerror monitor 24, as well as the number of errors that were corrected bythe FEC system 14. From this information, the monitor system 24 compilesstatistics at 106, such as information indicating temporal grouping orpacketizing or randomness of the errors, thereby allowing analysis ofwhether the errors are related to impulse noise, continuous noise, orboth. At 108, the analyzer system 26 in the first modem 10 analyzes theerror data and the compiled statistics to ascertain the existence andextent of any packetized errors, and may also characterize the relativefrequency or infrequency of occurrence of packetized errors.

Packetized errors include any errors attributable, in whole or in part,to impulse noise. For instance, many data errors occurring in a shortperiod of time (e.g., hundreds or even thousands of errors in onesecond) may be considered by the analyzer system 26 as packetized,whereby the analyzer 26 may presume at 108 that impulse noise isoccurring in the channel 4. In this regard, the error information andstatistics may cover or be evaluated with respect to a certain timeperiod of interest, for example, the most recent few minutes or hours,or any suitable time period, such that any noise protection changesbased thereon will be correlated to the current noise conditions in thecommunication channel 4. Moreover, the analyzer 26 may selectivelyrefrain from increasing impulse noise protection where it determinesthat detected impulse noise is occurring relatively infrequently. Thus,for example, if a burst of impulse noise related errors is the firstsuch event detected in a very long time, the analyzer 26 may decide notto make any changes, such that system efficiency is optimized whereimpulse noise related errors only occur once in a selectable long timeperiod.

At 110, the analyzer system 26 determines whether there are anyuncorrected packetized errors over the time period of interest(packetized errors are detected, which are not corrected by the forwarderror correction system 14). If not (NO at 110), the analyzer 26concludes that any packetized errors have been corrected, and a numberof corrected packetized errors in the relevant time period is checked at114. In this regard, it is noted that the number of FEC redundancy bytescurrently being employed in the system 2 are selected so as to be ableto correct for a certain number of error bytes per codeword. Thus, inone example the current FEC settings (e.g., number of redundancy bytes)may correct for N error bytes per codeword. The analyzer 26 maydetermine or be programmed with a threshold value against which tocompare the number of corrected packetized errors at 114, for example,N/2 or other threshold value. In this case, the analyzer 26 determinesat 116 whether the number of corrected packetized errors is less thanthe threshold value (including no packetized errors, where the number iszero). If not (NO at 116), the analyzer 26 concludes at 118 that thecurrent FEC/IL and codeword size settings are appropriate to the currentimpulse noise conditions in the channel 4, since all errors related toimpulse noise in the relevant time period are being corrected, and thecurrent impulse noise protection settings are not excessive (e.g.,little if any data rate sacrifice). In this case, the analyzer 26 leavesthe impulse noise protection settings unchanged at 118, and the method100 returns to impulse noise monitoring at 106.

If the number of corrected packetized errors is less than the thresholdvalue (YES at 116, including the case where the number is zero), theanalyzer 26 concludes that there may be excess impulse noise protectionrelative to the current impulse noise conditions in the channel 4. Inthis case, the analyzer 26 presumes that the current or recent impulsenoise in the channel 4 is small or negligible and the method 100proceeds to 140, where the FEC/IL/codeword size parameters are adjustedto reduce the amount of impulse noise protection and hence to improvethe data rate/system efficiency. Further details of the exemplaryimpulse noise protection decrease/efficiency improvement at 140 areillustrated and described below with respect to FIG. 5. Furthermore, theadjustment at 140 may be performed in concert with bit swapping, SRA, orother parameter changes directed to increasing or decreasing protectionagainst continuous noise, as illustrated and described further belowwith respect to FIGS. 6-7B. Thereafter, the method 100 returns tocontinue data error monitoring and statistical analysis at 106 and 108.

If there are uncorrected packetized errors (YES at 110), the analyzer 26checks the time duration since the last undetected error event at 112.In this regard, the fact that the analyzer 26 detects an uncorrectederror may not require a proposal to change the impulse noise protection,for example, where the detected packetized error represents a very rareevent. The analyzer 26 accordingly ascertains the relevant observationtime since the last detected uncorrected error, and if this time islonger than a threshold time value (e.g., as determined by Quality ofService (QoS) requirements for a particular service which may beprogrammable in the receiver modem 10, or as determined by othersuitable criteria), no increase in protection is needed. If this time isless than the threshold time value (YES at 112, e.g., less than theminimum time between two error events allowed by the specificrequirements for QoS), the analyzer 26 concludes that the currentimpulse noise protection settings are insufficient to combat errorsresulting from the current impulse noise conditions in the channel 4. Inthis case, the method 100 proceeds to 120, where the impulse noiseprotection settings (e.g., codeword size, FEC redundancy, andinterleaving depth) are adjusted to increase the impulse noiseprotection. Thereafter, the method 100 returns to 106 and 108 tocontinue monitoring and analyzing the error data and statistics. If thetime duration since the last uncorrected packetized error even issufficiently long (NO at 112), the method 100 proceeds to 118, whereinthe analyzer 26 concludes that the current FEC/IL and codeword sizesettings are appropriate to the current impulse noise conditions in thechannel 4, and leaves the impulse noise protection settings unchanged,after which the method 100 returns to impulse noise monitoring at 106.

FIGS. 4 and 5 illustrate further details of increasing impulse noiseprotection at 120 and increasing efficiency by decreasing unnecessaryimpulse noise protection at 140, respectively, in the method 100 of FIG.3. Once the analyzer 26 has determined that an increase in the impulsenoise protection is desired (e.g., uncorrected packetized errors inrather short time intervals have been detected, YES at 112 in FIG. 3),the exemplary analyzer 26 proposes increased interleaving, increased FECredundancy, or decreased codeword size in prioritized fashion, asillustrated in FIG. 4. The analyzer 26 initially determines at 122 inFIG. 4 whether the interleaving is currently maximized with respect tolatency limitations of the particular DSL service being provided, and/orwhether buffer memory limitations prevent further interleaving increase.In this regard, increasing the level or amount of interleaving will helpto prevent uncorrected packetized errors for a given amount of FECredundancy, but will result in increased buffer memory usage to storeoutgoing data being interleaved and incoming data being de-interleaved,and will also result in increased latency in delivering data across thecommunication channel 4. Accordingly, in this example memoryavailability and/or the amount of tolerable latency may limit the amountof interleaving that can be used in a given application.

If the current interleaving settings are not maximized with respect tosuch memory or latency limitations (NO at 122), the interleaving isincreased at 124 within such limits without DSL service interruption,and the impulse noise protection increase 120 is finished (e.g., themethod 100 returns to 106 in FIG. 3). The adjustments to increaseimpulse noise protection by increasing interleaving at 124, and/or thoseadjustments which increase FEC redundancy or decrease codeword sizebelow (e.g., as well as changes in FIG. 5 to decrease impulse noiseprotection), are accomplished in the exemplary system 2 by the analyzer26 proposing such parameter changes, and the local management systems 22and 42 exchanging messages, parameter values, and time markers 44through the local management channel 46 to implement the proposedchanges in a coordinated fashion without interrupting the DSLcommunication service.

If the interleaving settings are already maximized according to somepredetermined criteria (YES at 122), the analyzer makes a determinationat 126 as to whether the current FEC redundancy settings are maximized.If not (NO at 126), the number of FEC redundancy bytes is increased at128 (again without interrupting the communication service on the channel4), and the impulse noise protection increase 120 is finished. Changesto the FEC redundancy settings may be performed in any suitable mannerat 128 within the scope of the invention. However, if the current FECredundancy is already maximized (YES at 126), the analyzer 26 makes adetermination at 130 as to whether the current codeword size isminimized. If not (NO at 130), the codeword size is decreased at 132without service interruption, and the method 100 returns to 106 in FIG.3 to continue monitor and analyzing error data. If the codeword size isalready minimized (YES at 130), the analyzer 26 signals the localmanagement system 22 at 134 that the impulse noise protection is alreadymaximized, and the method 100 returns to 106 in FIG. 3.

FIG. 5 illustrates an exemplary prioritized implementation of theimpulse noise protection reduction at 140 of the method 100, wherein theanalyzer 26 recommends increasing codeword size, decreasing FECredundancy, or reducing the amount of interleaving if impulse noiseprotection reduction is appropriate according to the current impulsenoise situation in the channel 4. At 142 in FIG. 5, the analyzer 26determines whether the current codeword size is maximized. If not (NO at142), the codeword size is increased at 144 and the impulse noiseprotection decrease/efficiency improvement 140 ends. Thereafter, themethod 100 returns to 106 and 108 in FIG. 3 to continue monitoring andanalyzing the data errors and corresponding statistics.

If the current codeword size is already maximized (YES at 142 in FIG.5), the analyzer 26 makes a determination at 146 as to whether the FECredundancy is currently minimized (e.g., zero). If not (NO at 146), theFEC redundancy is decreased at 148, and the method 100 returns to 106and 108 in FIG. 3 to continue monitoring and analyzing the error dataand statistics. Otherwise (YES at 146), the analyzer 26 determineswhether the current interleaving is minimized (e.g., zero) at 150. If so(YES at 150), the analyzer 26 does not recommend any changes, as thesystem is already optimized for minimum impulse noise protection, andthe method 100 returns to monitor the error data at 106 in FIG. 3.Otherwise, (NO at 150), the interleaving is decreased at 152, and themethod 100 returns to 106 in FIG. 3. Other suitable adjustmentstrategies or protocols can be used for selectively increasing ordecreasing impulse noise protection, wherein the invention is notlimited to the specific implementations of FIGS. 4 and 5 or the orderingof the parameter adjustments thereof.

Referring now to FIG. 6, another aspect of the invention providesmethods for adjusting a communication system, wherein one such method200 is illustrated in FIG. 6. The method 200 may be implemented in anycommunication system, including but not limited to the exemplarymulticarrier DSL system 2 of FIG. 1. DSL initialization is carried outat 202, with protection parameters for impulse and continuous noisebeing initially set, after which DSL service begins at 204. The receiver(e.g., the first modem 10 in FIG. 1) monitors continuous and impulsenoise at 206, and determines whether adjustments are needed at 208 forimpulse noise protection, continuous noise protection, or both. Themonitoring at 206 may be carried, for example, by the noise and errormonitor 24 in the first modem 10, and the determination at 208 may bydone by the analyzer 26, with any proposed changes being provided to thefirst local management system 22 and from there to the management system42 of the second (e.g., transmitter) modem 30.

At 210, the local management system (either the first management system22 or the second management system 42 in FIG. 1) determines whether theproposed adjustments result in a data rate change, and if so, makes thecorresponding rate adjustments. At 212, the transmitter initiates therequested changes to the noise protection parameters withoutcommunication service interruption, with changes that cause data rateincreases being initiated prior to those that decrease the data rate,whereafter the method 200 returns to noise monitoring at 206. Inaccordance with an aspect of the invention, the coordinated adjustmentof the continuous and impulse noise protection parameters is performedat 212 so as to minimize redundancy in the system 2, and to therebyoptimize the data transfer rate.

FIGS. 7A and 7B illustrate a more detailed method 300 for adjusting acommunication system to adapt to changing impulse noise and/orcontinuous noise in accordance with the invention. At 302 in FIG. 7A,initial impulse and continuous noise protection parameters are set, andDSL service begins at 304. The receiver (e.g., the first modem 10 inFIG. 1) monitors the signal to noise ratio (SNR) for each subcarrier at306 during DSL service. In addition, the receiver monitors corrected anduncorrected errors as a function of time at 308, and collects orcompiles statistics for data transfer errors and SNR at 310. Asdescribed above, the noise and error monitor 24 and the analyzer 26 ofthe first modem 10 in FIG. 1 may perform the noise measurement andassessment acts at 306-310.

At 312, as determination is made as to whether the data errors arerandomly distributed over received codewords, and/or whether data errorsare concentrated in packets (e.g., packetized errors). If all the errorsare randomly distributed and no packetized errors were observed (NOPACKETIZED ERRORS at 312), a determination is made at 314 as to whetherthe subcarrier SNR values correspond with the data errors. If not (NO at314), the receiver recommends impulse noise protection changes at 320,and the method 300 proceeds to 330 in FIG. 7B, as described furtherbelow. If, however, there is certain correspondence between thesubcarrier SNR and the random errors (YES at 314), the receiverrecommends or proposes changes to the continuous noise protection at 318(e.g., bit swapping, rate adaptation, etc.), and the method 300 alsoproceeds to 330 in FIG. 7B.

If packetized errors are determined (PACKETIZED ERRORS at 312 in FIG.7A), the receiver determines at 322 whether the impulse noise protectionis set to it maximum value. If not (NO at 322), the receiver recommendschanges to impulse noise protection at 320 (e.g., without adjustments tocontinuous noise protection), and the method 300 proceeds to 330 in FIG.7B as described below. However, if impulse noise protection is set toits maximum value (YES at 322), the receiver recommends or proposeschanges to the continuous noise protection at 318 (e.g., changes in bitloading, mostly rate adaptation, but other adjustments may be made), andthe method 300 proceeds to 330 in FIG. 7B.

Referring now to FIG. 7B, where changes to one or more of the impulsenoise protection parameters and/or those affecting continuous noiseprotection are recommended by the receiver, the transmitter determinesat 330 whether the requested changes result in a different data rate. Ifnot (NO at 330), the transmitter initiates the requested parameterchanges at 332, for example, through messaging between the localmanagement systems 42 and 22 in FIG. 1 or other suitable protocol,wherein the changes may be implemented contemporaneously or certainchanges may be implemented before others. The method 300 then returns to306 in FIG. 7A and proceeds as described above. However, if therequested changes will result in a different data rate (YES at 330 inFIG. 7B), the transmitter first initiates the corresponding data ratechange at 334, for example, using rate adaptation or other suitable datarate adjustment techniques. At 336, the transmitter then initiatesadjustment of the requested parameters that result in data rateincrease, prior to initiating the parameter changes that result in datarate decrease at 338, after which the method 300 then returns to 306 inFIG. 7A and proceeds as described above.

Although the invention has been illustrated and described with respectto one or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurewhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations of the invention. Inaddition, while a particular feature of the invention may have beendisclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application. Furthermore, to the extent that the terms“including”, “includes”, “having”, “has”, “with”, or variants thereofare used in either the detailed description and the claims, such termsare intended to be inclusive in a manner similar to the term“comprising”.

1. A method for adaptive adjustment of a communication system, themethod comprising: monitoring impulse noise on a communication channelduring communication service; and selectively adjusting impulse noiseprotection according to the impulse noise without interrupting thecommunication service.
 2. The method of claim 1, wherein monitoring theimpulse noise comprises: monitoring data transfer errors occurring onthe communication channel; determining whether any of the data transfererrors are packetized errors; and determining whether any packetizederrors are corrected or uncorrected.
 3. The method of claim 2, whereinselectively adjusting the impulse noise protection comprises:selectively increasing the impulse noise protection without interruptingthe communication service if there are uncorrected packetized errorsduring a relevant observation time that is less than a threshold timevalue; selectively decreasing the impulse noise protection withoutinterrupting the communication service if there are no uncorrectedpacketized errors and if a number of corrected packetized errors is lessthan a threshold value; and leaving the impulse noise protectionunchanged if there are no uncorrected packetized errors and if thenumber of corrected packetized errors is greater than or equal to thethreshold value.
 4. The method of claim 3, wherein selectivelyincreasing the impulse noise protection comprises at least one ofincreasing interleaving, increasing redundancy, and decreasing codewordsize.
 5. The method of claim 3, wherein selectively increasing theimpulse noise protection comprises: selectively increasing interleavingif possible within interleaving limits; if increasing interleaving isnot possible, selectively increasing a number of redundancy bytes ifpossible within redundancy limits; and if increasing interleaving orredundancy is not possible, selectively decreasing codeword size ifpossible within codeword size limits.
 6. The method of claim 3, whereinselectively decreasing the impulse noise protection comprises at leastone of increasing codeword size, decreasing redundancy, and decreasinginterleaving.
 7. The method of claim 3, wherein selectively decreasingthe impulse noise protection comprises: selectively increasing codewordsize if possible within codeword size limits; if increasing codewordsize is not possible, decreasing a number of redundancy bytes ifpossible within redundancy limits; and if increasing codeword size isnot possible and if decreasing the number of redundancy bytes is notpossible, selectively decreasing interleaving if possible withininterleaving limits.
 8. The method of claim 3, further comprising:monitoring continuous noise on the communication channel during thecommunication service; and selectively adjusting continuous noiseprotection according to the continuous noise without interrupting thecommunication service, wherein the continuous noise protection and theimpulse noise protection are adjusted in a coordinated fashion tominimize redundancy.
 9. The method of claim 1, wherein selectivelyadjusting the impulse noise protection comprises: selectively increasingthe impulse noise protection without interrupting the communicationservice if there are uncorrected packetized errors on the communicationchannel during a relevant observation time that is less than a thresholdtime value; selectively decreasing the impulse noise protection withoutinterrupting the communication service if there are no uncorrectedpacketized errors on the communication channel and if a number ofcorrected packetized errors on the communication channel is less than athreshold value; and leaving the impulse noise protection unchanged ifthere are no uncorrected packetized errors on the communication channeland if the number of corrected packetized errors on the communicationchannel is greater than or equal to the threshold value.
 10. The methodof claim 9, wherein selectively increasing the impulse noise protectioncomprises at least one of increasing interleaving, increasingredundancy, and decreasing codeword size.
 11. The method of claim 9,wherein selectively increasing the impulse noise protection comprises:selectively increasing interleaving if possible within interleavinglimits; if increasing interleaving is not possible, selectivelyincreasing a number of redundancy bytes if possible within redundancylimits; and if increasing interleaving or redundancy is not possible,selectively decreasing codeword size if possible within codeword sizelimits.
 12. The method of claim 9, wherein selectively decreasing theimpulse noise protection comprises at least one of increasing codewordsize, decreasing redundancy, and decreasing interleaving.
 13. The methodof claim 9, wherein selectively decreasing the impulse noise protectioncomprises: selectively increasing codeword size if possible withincodeword size limits; if increasing codeword size is not possible,decreasing a number of redundancy bytes if possible within redundancylimits; and if increasing codeword size is not possible and ifdecreasing the number of redundancy bytes is not possible, selectivelydecreasing interleaving if possible within interleaving limits.
 14. Themethod of claim 1, further comprising: monitoring continuous noise onthe communication channel during the communication service; andselectively adjusting continuous noise protection according to thecontinuous noise without interrupting the communication service, whereinthe continuous noise protection and the impulse noise protection areadjusted in a coordinated fashion to minimize redundancy.
 15. A methodfor adaptive adjustment of a communication system, the methodcomprising: monitoring impulse noise on a communication channel duringcommunication service; monitoring continuous noise on the communicationchannel during communication service; and selectively adjusting impulsenoise protection and continuous noise protection parameters in thesystem according to the impulse noise and the continuous noise withoutinterrupting the communication service.
 16. The method of claim 15,wherein the impulse noise protection and the continuous noise protectionare adjusted in a coordinated fashion to minimize redundancy.
 17. Acommunication system, comprising: a communication channel; a first modemcoupled with the communication channel, the first modem being adapted tomonitor impulse noise on the communication channel during communicationservice; and a second modem coupled with the communication channel;wherein the first and second modems are adapted to cooperatively adjustimpulse noise protection according to the impulse noise withoutinterrupting the communication service.
 18. The communication system ofclaim 17, wherein the first modem is further adapted to monitorcontinuous noise on the communication channel during the communicationservice, and wherein the first and second modems are adapted tocooperatively adjust impulse noise protection and continuous noiseprotection in the system according to the impulse noise and thecontinuous noise without interrupting the communication service.
 19. Thecommunication system of claim 18, wherein the first and second modemsare adapted to cooperatively adjust the impulse noise protection and thecontinuous noise protection in a coordinated fashion to minimizeredundancy.
 20. The communication system of claim 17, wherein the firstmodem comprises: a monitor system that monitors data transfer errorsoccurring on the communication channel; and an analyzer system coupledwith the monitor system, the analyzer system being adapted to determinewhether any of the data transfer errors are packetized errors, and todetermine whether any packetized errors are corrected or uncorrected.21. The communication system of claim 20, wherein the first and secondmodems are adapted to selectively increase the impulse noise protectionif there are uncorrected packetized errors during a relevant observationtime that is less than a threshold time value, to selectively decreasethe impulse noise protection if there are no uncorrected packetizederrors and if a number of corrected packetized errors is less than athreshold value, and to leave the impulse noise protection unchanged ifthere are no uncorrected packetized errors and if the number ofcorrected packetized errors is greater than or equal to the thresholdvalue.
 22. The communication system of claim 17, wherein the first andsecond modems are adapted to selectively increase the impulse noiseprotection if there are uncorrected packetized errors on thecommunication channel during a relevant observation time that is lessthan a threshold time value, to selectively decrease the impulse noiseprotection if there are no uncorrected packetized errors on thecommunication channel and if a number of corrected packetized errors isless than a threshold value, and to leave the impulse noise protectionunchanged if there are no uncorrected packetized errors on thecommunication channel and if the number of corrected packetized errorsis greater than or equal to the threshold value.
 23. A modem,comprising: a transceiver that is coupleable to a communication channel,the transceiver being adapted to support communication service with asecond modem on the communication channel; a monitor system coupled withthe transceiver, the monitor system being adapted to monitor datatransfer errors occurring on the communication channel duringcommunication service; and an analyzer system coupled with the monitorsystem, the analyzer system being adapted to determine whether any ofthe data transfer errors are packetized errors, and to determine whetherany packetized errors are corrected or uncorrected; wherein the analyzeris further adapted to propose impulse noise protection adjustments tothe second modem according to the impulse noise and to cooperativelyadjust impulse noise protection according to the impulse noise withoutinterrupting the communication service.
 24. An adjustment system foradaptive adjustment of a communication system, the system comprising:means for monitoring impulse noise on a communication channel duringcommunication service; and means for selectively adjusting impulse noiseprotection according to the impulse noise without interrupting thecommunication service.
 25. The adjustment system of claim 24, whereinthe means for monitoring the impulse noise comprises: means formonitoring data transfer errors occurring on the communication channel;and means for determining whether any of the data transfer errors arepacketized errors, and for determining whether any packetized errors arecorrected or uncorrected.
 26. The adjustment system of claim 24, whereinthe means for selectively adjusting the impulse noise protectioncomprises: means for selectively increasing the impulse noise protectionwithout interrupting the communication service if there are uncorrectedpacketized errors on the communication channel during a relevantobservation time that is less than a threshold time value; means forselectively decreasing the impulse noise protection without interruptingthe communication service if there are no uncorrected packetized errorson the communication channel and if a number of corrected packetizederrors on the communication channel is less than a threshold value. 27.The adjustment system of claim 24, wherein the means for selectivelyincreasing the impulse noise protection is adapted to selectivelyincrease interleaving if possible within interleaving limits, or ifincreasing interleaving is not possible, to selectively increase anumber of redundancy bytes if possible within redundancy limits, or ifincreasing interleaving or redundancy is not possible, to selectivelydecrease codeword size if possible within codeword size limits.
 28. Theadjustment system of claim 26, wherein the means for selectivelydecreasing the impulse noise protection is adapted to selectivelyincrease codeword size if possible within codeword size limits, or ifincreasing codeword size is not possible, to decrease a number ofredundancy bytes if possible within redundancy limits, or if increasingcodeword size is not possible and if decreasing the number of redundancybytes is not possible, to selectively decrease interleaving if possiblewithin interleaving limits.
 29. The adjustment system of claim 24,further comprising: means for monitoring continuous noise on thecommunication channel during the communication service; and means forselectively adjusting continuous noise protection according to thecontinuous noise without interrupting the communication service, whereinthe continuous noise protection and the impulse noise protection areadjusted in a coordinated fashion to minimize redundancy.